As of 2021 there were 45,930 people employed as Helpers--Pipelayers, Plumbers, Pipefitters, and Steamfitters within the United States.
This represents around 0.03% of the employed workforce across the country.
Put another way, around 1 in 3 thousand people are employed as Helpers--Pipelayers, Plumbers, Pipefitters, and Steamfitters.